so I am very new to this. I am 17 and am doing a S4 TII conversion on a 1986 RX7 that had a blown motor. This project is for my Senior project to graduate high school... Ok so today I finally got the ECU and Wiring harness which I have been waiting for, for like 5 weeks! Originally I had planned to get a S5 motor but I ended up with a S4 but not sure if it is a 87 or 88. I know there are differences with the wiring harness and ECU with the two years even thought hey are both S4. But the ECU and harness I got is made for a S5. The ECU is N380 but that isn't my concern I already am getting a S4 ECU next week. But the wiring harness is what I am concerned about. Is there a way that I can make this harness work with the S4 engine I have. The harness is really expensive I know and hard to find..... So is there a way? The ECU and harness is the last thing I need to do for my car to run!

 

Throw away or sell the S5 ECU and harness. Do not buy a turbo EM harness.
Use your series four N/A harness.

Remember, whether n/a or turbo, they all have four injectors, a boost sensor, afm, water thermo sensor, alternator plug, ACV solenoids, same solenoids on that rack on the left of the engine, tps plug etc.

The n/a EM harness will work with MINOR changes. A Turbo EM harness would require more changes than a stock n/a harness. The secondary injector plugs will have to be routed just a little different on the turbo engine. Not a big deal.

Download the wiring schematics for the turbo and the n/a and also download from the Fuel section the pages called CONTROL UNIT for both the Turbo and the N/a engine. You can compare each pin of the ECUs and you'll be pleasantly surprised to find few differences b/t the two. Talking S4 cars.

 

Ok I Sold offmy n/a harness and everything. It had the maf sensor I think and all. The sensor that plugged into the air sensor. I think I may have made a mistake. What do I do? Do U know where I can buy a n/a harness for cheap. I'm getting an ecu for the S4 next week I already bought it. It came off an 88 TII. The engine I have is JDM... So I don't have to worry if the harness is JDM or US spec. If there is a guide that can help me with my problem please tell me.... I really want to finish this damn project.... Thanx for the help!!!!!

 

Not to be rude, but if you go to the SEARCH engine at the top of the page and put in TURBO SWAP you'll get any number of hits and you might read them for information. I did that a moment ago and got this: https://www.rx7club.com/forum/search...archid=2354756

Also at the very first page, at the top there is a thread saying something about FAQ. You might read that and look for the remarks about swaps.

You really should be swapping in a turbo transmission also. I saw no mention of that. It can be done without doing that bur its some more complications.

Parts, used parts, can be bought on this fourm. Look for the FOR SALE section and make a listing.

 

I got the transmission and engine in one piece. So I have the turbo engine and tranny. So yeah thanks for the info about the sales thing. I'm really new to this.... and reading is not exactly my strongest point. LOL

 

Be glad that you didn't get the s5 13bt. You would have a wild time trying to wire that sucker in.

That is, unless you go standalone, like I'm gonna do.

 

Then just get the n/a harness and change the engines and plug the harness in. By the way, you will need a turboII transmission mount. The na one won't work. Hope it came with the enine/transmission.

You'll also need a driveshaft workaround. The n/a shaft won't connect into the turbo transmission. Either a local shop can make you a drveshaft or you can buy one ready made from Mazdatrix.com

YOu NEED a TURBO boost sensor. The n/a one is what they call a ONE BAR sensor and the tubo one a TWO BAR one. It really makes a big difference.

 

I have everything. I got the TII driveshaft, LSD whole differential, TII engien and Tranny with mounts, and all I'm trying to do is get the ECU running. I'm getting an 88 TII ecu next week and I'm just having problems with the harness its so damn hard to locate a S4 TII harness. My question is I'm not sure if my engine is an 87 or 88 I know they have differnt fuel injectors. Low and high impact. Is that so big of a deal? And I can get ahold of a N/a harness no problem but how do I get that to work for my Turbo engien the N/a doesn't have boost sensor and other stuff right?

 

its low and high impedance, and as long as you get a wiring harness that matches the injectors, you're fine. from what I recall, the 88 harness & injector plugs are red, rectangular inside (as opposed to oval for S5's), with a little tab thats offset from the center, and the 87 injectors are a different color (tan maybe), rectangular, with a centered tab.

 

The na has a pressure sensor and the turbo a boost sensor. Same location, same plug and the wires begin and end in the same locations. You need to put a turbo boost sensor in place of the pressure sensor.

Again, n/a and turbo have FOUR INJECTORS, A BOOST/PRESSURE SENSOR, AFM, WATER THERMO SENSOR AND THE SAME SOLENOIDS ON THE RACK(plus one more on the turbo) and the n/a EM harness has a plug for the alternator whereas the turbo EM harness does not have a plug for the alternator. Life does not get much simpler than that.

So, go ahead and install a TurboII EM harness. Now you get to make/route the non existant alternator wire, you get to unscramble the two plugs on the EM harness called FEM-01 and FEM-02. You unscramble them because once you install that Turbo EM harness and mate it with a N/A EM harness you lose your water temp gauge reading and the oil temp gauge reading unless you take action to reroute the wiring at the two plugs mentioned just above.

With a stock n/a harness you DO have to make a change or two. Like the twin scroll solenoid that is on the turbo needs two wires routed about a foot from an existing plug on the n/a harness to that solenoid. Good golly miss molly.

THere's too many threads on swaps to continue with this. Sameo sameo. This swap stuff is only rivaled by SETTING THE TPS. EEEEEEEK! Aaaaargh! s e a r c h

And get a turboII afm to go along with the other stuff if you don't already have it (same location as the n/a afm, same wires, same begin and end for each wire. Life is good.

 

Ok I'm gonna take picture of the injectors and post it. I looked at them adn they looked purple but I'll remove the manifold and take good picture....

 

I believe the later s4's are purple, and the earlier ones are red. The harness and connectors are the same, but I think you need to remove the resistor back from your 86. That or you need to put one in. Its late and I can't think straight, so hopefully someone else will straighten it out. Maybe search for "high imp injector resistor" or something like that.